An environment-friendly vehicle, which uses an engine and a motor as a driving power source, includes a battery for driving the motor. A battery safety device or a battery system main relay (SMR) of using a main relay is installed between a battery terminal and a power line to safely supply battery power.
Referring to FIG. 2, a battery safety device according to the related art includes three main relays 1, 2, and 3 and one resistor 4. The first and second main relays 1 and 2 are connected to a positive terminal of the battery 5 and the third main relay 3 is connected to a negative terminal of the battery 5. The resistor 4 is connected in series to the first main relay 1 which is connected to the positive terminal of the battery 5.
As the first to third main relays 1 to 3 are turned on one by one when the battery SMR is powered on, that is, the battery power is supplied to the power line, as shown in following Table 1, the battery safety device according to the related art detects failure, such as a welding failure of the main relay and an operational failure, through the initial step to third step.
TABLE 1ConditionVp = 00 << Vp << VbatVp = VbatInitial stepNormalSMR1 & 3 WeldSMR1 & 2 & 3 weldor SMR2 & 3 weldFirst stepNormalSMR1 weldSMR2 weldSecond stepSMR1 Non-NormalSMR2 weldoperation orSMR3 Non-operationThird step—SMR2 Non-NormaloperationFourth step——Normal
As shown in Table 1, since all of the main relays are not operated in the initial step, if a measured voltage Vp of the power line is higher than ‘0’ and lower than a battery voltage Vbat, a welding failure of the first and third main relays 1 and 3 is detected. When the measured voltage Vp is equal to the battery voltage Vbat, the welding failure of the first to third main relays 1 to 3 is detected.
Since the third main relay 3 is turned on in the first step, if the measured voltage Vp of the power line is higher than ‘0’ and lower than the battery voltage Vbat, a welding failure of the first main relay 1 is detected. When the measured voltage Vp of the power line is equal to the battery voltage Vbat, a welding failure of the second main relay 2 is detected.
Since the first main relay 1 is turned on in the second step, if the measured voltage Vp of the power line is equal to ‘0’, an operational failure of the first or third main relay 3 is detected. When the measured voltage Vp of the power line is equal to the battery voltage Vbat, the welding failure of the second main relay 2 is detected.
An operational failure of the second main relay 2 is detected if the measured voltage Vp of the power line is higher than ‘0’ and lower than the battery voltage Vbat, since the second main relay 2 is turned on in the third step.
However, the battery safety device according to the related art cannot independently detect a welding failure of the third main relay 3 when the battery SMR is powered on. In addition, the battery safety device according to the related art cannot independently detect an operational failure of the first and third main relays 1 and 3.